Process for refining mineral oils



Patented Aug. 29, 1944 James V. Montgomery, Okmulgee, kla., Luke Barrett Goodson, Borger, Tex., and Robert W. Henry, Bartlesville, 0kla., assignors to Phillips Petroleum Company, a corporation of Delaware N 0 Drawing.

Application August 23, 1940,

Serial No. 353,956

6 Claims.

by Donath, Zeit. fiir Angewandte Chemie 19,

657-668 (1906) by Bedson, J. Soc. Chem. Ind., 27, 147-150; Hofmann and Damm, Brennstoff Chemie, 4, 65-73; and others. The use oi-pyridine in the solvent fractionation of hydrocarbon oils was disclosed by German Patents 319,656 (1918) and 372,208 (1921), and by the French Patent 593.502 (1924). Poole, in Ind. and Eng. Chem. p. 170-177 (1931), discussed the solubility of oil and wax in various solvents, including pyridine. Ferris et al., Ind. and Eng. Chem. p. 753-761 (1931), reported the investigation of a large number of organic compounds, including pyridine, quinoline and alpha picoline. These materials investigated by Ferris evidently contained some water since the temperatures for complete miscibility with 25 A. P. I. gravity oil of 0.851 viscosity-gravity constant, were quite high, as 77 F. for pyridine, 58 F. for quinoline, and 86 F. for alpha picoline, whereas anhydrous pyridine and picolines are miscible with such an oil at temperatures slightly below 0 F. Numerous United States and foreign patents have been issued covering the use of unsaturated heterocyclic nitrogen compounds for the solvent extraction and solvent dewaxing of mineral oils. Careful examination, however, reveals that in all cases these solvents were restricted in their usefulness as dewaxing solvents by a relatively low solubility for the oil component, as well as for the wax component, particularly at the low temperatures suitable for dewaxing mineral oils to the low pour points required for commercial util ity. In all cases where solvent dewaxing of high viscosity index oils to low pour points (0 F. and below) was attempted, it was necessary to use solubility enhancers'to hold the oil in solution. The use of these solubility enhancers resulted in a large differential between the dewaxing temperature and the pour point of the dewaxed oil since such materials in themselves have an appreciable solubility for wax even at the dewaxing temperatures.

One object of thisinvention is to provide a group of new and improved selective solvents for use in lubricating oil refining.

Another object of this invention is to provide a dewaxing solvent in which oil and wax are miscible at normal atmospheric temperatures and in which the oily constituents are miscible at dewaxing temperatures;

Another object is to provide a dewaxing solvent in which the wax constituents are relatively insoluble at dewaxing temperatures.

Still another object of this invention is to provide a solvent which maybe used advantageously with-antisolvents for dewaxingand for extraction.

Still other objects and advantages will be apparent from a studyof the disclosure which follows.

We have discovered that the saturated or partially saturated heterocyclic nitrogen bases are miscible with petroleum oils at much lower temperatures than are the corresponding unsaturated compounds. For example, the pipecolines or saturated picolines (prepared by hydrogenating the 240-500 F. fraction of commercial pyridine, which fraction of commercial pyridine is composed substantially of picolines), are completely miscible with a treated dewaxed Mid- Continent residual lube stockof 90 S. U. V. at 210 F. and V. 1., at 35 F., while a mixture of a similarly selected cut of anhydrous picolines and this same Mid-Continent oil separated into two phases upon cooling the mixture to +5 F. These saturated and partly saturated heterocyclic nitrogen bases have complete solubility for oil and wax at elevated temperatures and show marked anti-solvent powers for wax at lowtemperatures, with complete solubility for the oil component, thus making them excellent solvents for use in the solvent dewaxing-oi mineral oils to produce useful oils of lowpour point. The addition of hydrogen to the unsaturated nitrogen compounds has increased their miscibility with hydrocarbon oils at low temperatures. These saturated and partially saturated bases include such compounds as piperidine, pyrroline, pyrroli dine, hydrogenated pyridines, pyrazoline, pyrazolidine, etc., and their alkyl derlvatives, as the pipecolines, methyl pyrrolidinea -etc As an additional advantage, we have found that while the unsaturated bases such as picolines are completely miscible with water the corresponding saturated compounds, the pipecolines,

are not miscible with water in all proportions. For example, the addition oitwo volumes of water [with some other nitrogen base compounds in smaller proportions. The hydrogenation of this "240-500" F. commercial pyridine fraction lowers the boiling range of the fraction to approximately 215-450 F., since the boiling points ofthe hydrogenated pyridine, picolines, quinolines, etc., are ordinarily 10-60 F. lower than the boiling points of the unhydrogenated parent com pounds, for example:

Corresponding hydrogenated nitrogen base, B. P.

Unsaturated heterocyclic nitrogen base, B. P.

F. F. Pyridine 239 .Piperidine 223 Alpha picoline 264 2 methyl piperidine 246 Beta picoline 290 3'methyl piperidine. 259 Gamma picoline 289 4 methyl piperidine 264 Quinoline 457 Deca-hydro quinoline 400 10% cut'No.

It might be mentioned that some commercial pyridines contain much higher boiling material than the above given example.

We have found'that when" desired, the above mentioned saturated and partially saturated heterocyclic nitrogen containing compounds, as the pipecolines, may be used with known wax antisolvents, such as low boiling alcohols, acetone, methyl ethyl ketoneand/or other aliphatic or aromatic ketones, aniline nit-robenzene, pyridine, picolines, pyrrol; etc., to give exceptionally low pour point oils. 7

It should be added that a blend of pipecoline with furfural or phenol would not be a satisfactory solvent since pipecoline reacts with these two materials to formcomplex dye-like-substances which are not stable to distillation;

Acetone is recognized as an ideal antisolveht for wax. Wyant and March, Bureau of Mines, Technical Paper 368 (1925), found acetone to be well adapted to the separation of Wax from oil and listed among its advantages:

(1) Oil and wax completely soluble in acetone at 100 F.

(2) At temperatures below 90 -F., the separation of wax and solvent is sharp.

(3) The solubility of commercial wax is very low at temperatures of 50-70 F.

(4) The wax crystals are large and easily filterable.

(5) Acetone boils at a low temperature, 134 F., and it may be completely removed from the oil.

Acetone, however, has a very low solvent power for oil and for this reason it is not practical to attempt to manufacture lubricating oils of low pour point, such as 0 F. or below, by the use of acetone alone as a dewaxing solvent since the oil-wax-solvent mixture separates into two liquid phases at low temperatures. The oil phase is highly viscous and filtration of wax from this phase is diificult. This disadvantage has been overcome by blending supplementary solvents or solvent enhancers with the acetone to hold the oil in solution. Examples of materials suitable for use as solubility enhancers are: petroleum naphthas, benzene, toluene, isopropyl ether, etc. Unfortunately, however, these materials have a rather high solubilityfor wax as well as for oil at the dewaxing temperatures. When the solvent is removed from the oil after the dewaxing operation, this dissolved wax remains in the oil, resulting in an oil of high pour point, or a large difierential between dewaxing temperatures and the pour point of the recovered oil. As examples of such blends, the following experiments are cited:

(1) One volume of treated dewaxed Mid-Continent lubricating oil stock of 90 S. U. V., at 210 F. and V. I., was mixed with one volume of a solvent composed of 40% acetone, 40% benzol and 20% toluol. A phase separation occurred on chilling to +10 F.

(2) One volume of treated dewaxed Mid-Continent lubricating oil stock of S. U. V., at 210 F. and 85 V. I., was mixed with one volume of a solvent composed of 30% acetone, 50% benzol and 20% toluol. A phase separation occurred at, -l5 F,

(3) One volume of treated waxy Mid-Centhnent residual lubricating oil stock was mixed with, four volumes of a'solvent composed of 30% ace-.v tone, 50% benzene and 20% toluol, chilled to. 0 F. and filtered. The recovered oil was of +15?" F. pour point, 88 V. I., and83 S. U. V. at 210 Thus, the maximum proportion offacetone; which could be used in the solventfiqrydewax ing at 0 F. was about 30%, and under these con,-. ditions the solubility of the waxat 0 F. was sufiiciently high as to give aj+15 F. pour point on the recovered oil. Furthermore, when benzene alone is used as a diluent, ittends to crystallize out of solution at low temperatures. When a third component such as 'toluolis used to prevent the freezing out of the benzol the resulting three component mixture is difficult to maintain in the proper. ratio due to difference in boiling points and water solubility of the three components. When attempts are made to blend acetone with th more selective solvents, such as furfural, nitrobenzene, phenol, chlorex,- pyridine, etc., the resulting solution has such a low solvent power for oil at low dewaxing temperatures that dewaxing can be carried out only athigh temperatures with the-productionoffhigh index oils at to F. For example:

(1) One volume of treated dewaxed Mid-Continent residual lube stock of 90 S. U. V. at'210 prepared by hydrogenating the dewaxing;

three volumes of a solvent composed of acetone and 60% pipecolines prepared as in above Exampl 1. The solution was mixed thor-.- oughly, shock chilled to 0 F., filtered and the solvent removed by distillation. An oil of 0 1F. pour point was obtained.

'Thus while it is known to mix as much as 40% acetone with such auxiliary solvents as naphtha, acetone and benzol, such solvents are limited in use with medium and high V. -I.-oils to dewaxing temperatures above 0 F. Moreover, the benzol is non-selective, and is difficult to keep in solution at low temperatures. It has not heretofore been known to blend as high as 40% acetone with selective type solvents for use in dewaxing at 0 F. and below, dueto miscibility considerations. With our selective solvents comprising large proportions of acetone, it is possible to realize all the advantages of acetone dewaxing without the disadvantage of low solubility for oil, and at the same time theacetone is assisted in its wax precipitating action by the selective solvent which has a relatively high anti-solvent power for wax. With these blended solvents, itis possible to produce low .pour points oils with practically no difierential between the dewaxing temperature. and the pour point of the recovered oil. Moreover, the wax crystals formed from our blended solvent are distinct, sharp edged, and filtration is readily accomplished at high rates. Thus, as an additional contribution to the art, our invention discloses a method wherein the utility of acetone in solvent dewaxing is widely extended.

Weir, U. S. Patent 2,154,190, disclosed the use of blends of 40% nitrobenzene with 60% of anhydrous pyridine as, a dewaxing solvent. This blend was claimed to have exceptional properties as a dewaxing solvent since the resulting dewaxed oils were stated to be of lower pour point than the dewaxing temperature. He was restricted, however, to dewaxing temperatures of -50" F., and higher, since at lower temperatures an oil phase separated clue to the low solubility of the blend for oil.

Our investigation disclosed the following:

(1) One volume of anhydrous picolines (commercial pyridine, dried and fractionated to 250-300 F.) was mixed with one volume of treated dewaxed Mid-Continent residual lubricating oil stock of 90 S. U. V. at 120 F.and 85 V; I." On. chilling anoil phasefseparated at +6 F.

(2) -One volume of a' solvent composed of anhydrous picolines mentioned in (1) and 40% nitrobenzene, was mixed with one volume of the above dewaxed'lubricating on stock. On cool-- ing, a phase separation occurred at 50. F.

'(3) One volume of .asolvent composed of 60% anhydrous pipecolines (hydrogenated picolines prepared by hydrogenation of the picoline fractionmentioned in (1) above) and 40% nitrobenzene, was mixed with one volume of the above dewaxed lubricating oil stock. On chilling, a phase separation occurred at 0 F.

Thus' we are enabled to dewax at temperatures as low as 0 F. using a blend of 40% nitrobenzene with 60% pipecolines (hydrogenated picolines). By so operating, we have greatly extended the utility of nitrobenzene in solvent This invention is not to be limited in any mannor by the heretofore given examples which are for purposes of illustration only. It should be understood that the alkyl derivatives of the above saturated or partly saturated heterocyclic. nitrogen compounds are closely related in physical and chemical properties and that these derivatives singly or in mixtures which exist in suitab-le'boiling point range, for example, 240-500 F., =and melting point range suitable-for use at dewaxing temperature, as topermit separation from oil and wax, are satisfactory within degree for use as given.

Mixtures of these materials and similar materials are suitable. Such mixtures may be obtained by hydrogenation of commercial pyridine-picoline's, quinolines, selected cuts of nitrogen compounds from coal taroils, or hydrogenation of the nitrogen bases recovered from petroleum. A convenient method of obtaining useful dewaxing solvents consisting of blends of saturated and partially saturated heterocyclic nitrogen bases in pyridine, picoline, quinoline, etc., is to hydrogenate by conventional methods the said .pyridine, picoline, quinoline, etc., to such an'extent as to produce a mixture comprising hydrogenated and partially hydrogenated compounds. --.The solvent mixtures and solvent concentrations may be varied and used in many Ways as will be understood bythose skilled in the art. By increasing the proportions of antisolvent inthe mixtures, the resulting solvent may be used advantageously for solvent extraction of mineral oils at convenient temperatures, such as atmoslows:

A sample of Mid-Continent bright stock was batch extracted at 86 F. with 4 volumes of our blended solvent (25% pipeooline prepared as above disclosed,- and 75% acetone). Yields and tests on the stock and resulting products are:

It will be noted that by the use of our hydrogenated solvent with acetone, a raffinate possessing markedly improved qualities over those of the original stock was obtained.

A. suggested application of solvent extraction and solvent dewaxing of a lube oil stock with a solvent comprising a blend of acetone and pipecoline includes th following steps:

1. Extraction with. blended solvent: 75% acetone, 25% pipecoline, prepared as above disclosed.

2. Partial distillation of solvent from the rafilnateto remove a portion of the acetone, which step also removes. the water from the rafilnate solution.

3. Addition of sufficient pipecoline to bring the solvent composition to that desired for dewaxing, say about 40%. acetone and 60% pipecoline.

4. Dewaxing of the extracted raffinate with said dewaxing solvent blend.

The use of regulated quantities of water in selective solvents, partially or completely miscible withwater, for the purpose of regulating the solvent power of the mixture is known. Useful solvents. may be obtained by the use of regulated quantities of water in the above listed materials disclosed in our invention.

We, do not wish to be limited by the particular examples of dewaxing and extraction solvents, or blends of solvents and antisolvents or solubility enhancers, as given heretofore, since many materials and combinations of materials having the above-described characteristics and properties may be successfully employed in practicing our invention and yet remain within its intended scope.

We claim:

1. The process of dewaxin-g mineral oils including the steps of mixing the waxy oil with a dewaxing solvent comprising. a hydrogenated ,selected fraction of commercial pyridine, the selected fraction of commercial pyridine boiling between the approximate limits of 240 F. and 500 F., chilling the mixture of waxy oil and solvent to precipitate the wax and removing; the precipitated wax and the dewaxing. solvent from the dewaxed-oil.

2. The process of dewaxing mineral oils including the steps of mixing the waxy oil with a dewaxing solvent comprising a hydrogenated selected fraction of commercial pyridine, the selected fraction of commercial pyridine boiling between the approximate limits of 240 and 500? F.

and consisting essentially of picolines, chilling the mixture of waxy oil and solvent to} precipitate th wax, and-removing the precipitated wax and the dew-axingsolvent from the dewaxed oil.

3 The process of dewaxing mineral oils including the steps of mixing the waxy oil with a. tie-waxing solvent comprising a hydrogenated selectedfraction of commercial pyridine, this hy-.

drogenatedfraction of commercial pyridine consistingessentially of pipecolines, chilling the mixture of; waxy oil and solvent to precipitate the wax; and removing the precipitated wax and the dewaxingsolvent from the dewaxed oil.

4. The process of dewaxing mineral oils includingthe steps of mixing the waxy oil with a. dewax-ing solvent solution comprising a hydrogenated selected fraction of commercial pyridine and a wax antisolvent, the selected fraction of commercial pyridine boiling between the approximate limits of 240 F. and 500 F., chilling the mixture of waxy oil and solvent solution to precipitate the wax and removing the precipitated wax and the solvent solution from the dewaxed oil 5. The process of dewaxing mineral oils including the steps of mixing the waxy oil with a dewaxing solvent solution comprising a hydrogenated selected fraction of commercial pyridine and a wax antisolvent, the selected fraction of commercial, pyridine boiling between the approximate limits of 240 F., and 500 F. and consisting essentially of picolines, and the wax antiof commercial pyridine consisting essentially of pipecolines' and the wax antisolvent being. acetone, chilling the mixture of waxy oil and dewaxing solvent solution to precipitate the wax; andremoving' the precipitated wax and dewaxing solvent solution from the dewaxed oil.

JAMES v. MONTGOMERY. L. BARRETT G'OODSON. ROBERT W. HENRY. 

